Handling devices to facilitate the testing of SIMM's are currently known in the prior art, and have been available for a number of years. Examples of such prior art handling/testing devices include the DM 718 Simm Handler manufactured by Computer Service Technology, Inc. of Dallas, Tex.; the "Model 828-MCM" handler/tester manufactured by MC Systems, Inc. of Dallas, Tex.; the "3000 B" handler/tester manufactured by Exatron of San Jose, Calif.
The prior art SIMM handlers are substantially similar to each other with respect to their constructional details and operational methodology. As will be discussed in more detail below, though accomplishing the task of testing SIMM's, such prior art handlers possess certain deficiencies which detract from their overall utility, such deficiencies being related to the cost, reliability, and accuracy thereof.
The SIMM handlers constructed in accordance with the prior art (with the exception of the Exatron handler) typically include magazine trays of several sizes, each of which is adapted to accommodate a SIMM circuit board of a corresponding width. In such handlers, the circuit boards are dropped from a respective magazine tray onto a conveyer which is driven by a stepper motor. A nub on the conveyor forces the dropped circuit boards through a guide platform, thereby positioning the boards on the conveyor in a lengthwise (i.e., longitudinal) orientation. After traveling longitudinally along the conveyor, the circuit boards abut a retractable, adjustable pneumatic stop which facilitates the proper positioning thereof under a test connector. To prevent any damage to the conveyor or the circuit boards, the motion of the conveyor must stop precisely when a circuit board contacts the pneumatic stop. As such, the timing between the abutment of a circuit board against the pneumatic stop and the discontinuation of the conveyor motion is critical.
The Exatron handler also requires the longitudinal movement of the circuit board which is gravity fed into a contactor region without the use of a conveyor. In this particular handler, the circuit boards are loaded thereinto in a manner wherein they are oriented with their longitudinal axes angled upwardly into a slotted tray. The slotted tray employs the use of stepper motor control to index a gravity fed track which feeds the circuit boards longitudinally into the contactor region where they are tested with custom contacts. Subsequent to being tested, the circuit boards are released from the contactor region and sorted into pass or fail directions via a gravity fed sorting flipper mechanism.
In addition to the importance of stopping the conveyor motion precisely when a circuit board abuts the pneumatic stop (in handlers other than for the Exatron), the placement accuracy of each circuit board under the test connector in all prior art handlers must be precisely adjusted to insure that the test fingers of the test connector are precisely aligned with the electrical connection pads on the circuit board. In the prior art handlers, when the circuit board reaches a proper position relative to the test connector, a sensor is triggered which facilitates the actuation of the test fingers into contact with the connector pads of the circuit board. When the test fingers have been placed into contact with the connector pads, a ready signal is sent to the test connector, thus initiating a desired testing protocol. Subsequent to the completion of such testing protocol, a "sort good" or a "sort bad" signal is generated, with the test fingers then being moved away from the circuit board and the conveyor being reactivated to facilitate the movement of the tested circuit board lengthwise into a sort section of the handler.
In the sort section of the prior art handlers, a sorting mechanism is provided for sorting the tested circuit boards into respective ones of a pair of bins, depending on whether a "sort good" or a "sort bad" signal has been generated by the test connector subsequent to the completion of the testing protocol. Typically, these bins are located on one side of the handler, and are either stacked or disposed in side-by-side relation to each other. In those prior art handlers wherein the bins are disposed in side-by-side relation to each other, the sorting mechanism typically includes a sort tray or sort arm which rotates about a vertical axis to direct each circuit board into the proper bin upon exiting the handler. In those prior art handlers wherein the bins are stacked, the sort tray or sort arm typically rotates about a horizontal axis and stops in alignment with one of a pair of exit chutes, each of which communicates with a respective one of the stacked bins. The exit chutes are often provided with sort verification sensors which are tripped by the circuit boards as they pass therethrough.
Perhaps the most significant deficiency of the prior art handlers is that the circuit boards travel lengthwise (i.e., longitudinally) therealong in only one direction and at only one height. As such, these handlers are exceedingly large, and must be sized having a width which is at least four times the length of the circuit board to properly accommodate the magazine, testing, sort, and chute sections of the handler. A further deficiency is that the prior art handlers are overly complex in construction, and necessitate the inclusion of numerous operating and coordinating elements. As such, these handlers require excessive manual set-up time, and are highly prone to misalignment during the testing operation, general failures, and high maintenance downtime.
Indeed, recent experience in high volume production of SIMM circuit boards has indicated that these prior art handlers experience frequent jamming, thereby requiring human intervention to resume normal operation. Such jams occur when two (2) circuit boards are dropped from the magazine tray instead of a single circuit board, and by warped boards failing to pass through the guide platform when contacted by the nub on the conveyor. In the prior art handlers, jamming is also often attributable to the lack of sufficient circuit board guidance or containment mechanisms, and the need to precisely recalibrate the guides for each new circuit board width of differing circuit boards which are tested in the handler. When jams occur, the operator is typically alerted thereto by the sound of the conveyor continuously trying to force movement of the circuit boards into a particular location within the handler. Jams also commonly occur in the sort section of the prior art handlers. The prior art handlers are typically not adapted to shut down when a jam occurs, thus often resulting in damage to the circuit boards.
As will be recognized, the jamming of the prior art handlers results in the added cost of damaged boards, as well as labor to clear the jams. Additionally, quality problems result from circuit boards damaged by jams, with the test fingers of the test connector also often being damaged by jammed circuit boards, thus requiring frequent replacement which is extremely costly and time consuming. Moreover, the jamming of these handlers often results in a "bottleneck" in the normal flow of work in the manufacturing plant.
Adding to the extreme complexity of the prior art handlers is their construction from a combination of electromechanical and pneumatic components, including stepper motors and conveyers in addition to pneumatic actuators. Such construction causes the handlers to be noisy, bulky, slow acting, large in size, and susceptible to frequent down time. In these prior art handlers, little provision is made for machine action alteration due to malfunction, with such handlers further being difficult to set-up and load for circuit boards of differing sizes. In this respect, such set-up normally requires the use of magazine trays of several different sizes and the completion of many small adjustments to the handler. With particular regard to the Exatron handler, the same is extremely expensive to manufacture due to its use of multiple stepper motors and the necessity of having to accurately control and coordinate the movements of many moving parts. The Exatron handler is also significantly larger in size than prior art conveyor style handler/testers, with the major disadvantages of the Exatron being that it is extremely oversized, overpriced, overly complex, and of limited capability.
A further deficiency with prior art handlers is their lack of reliability in sorting due to the proximity of the receiving bins thereto, the small angle and distance between the exit chutes, and an overall poor design of the sorting mechanism. The mechanical reliability of the prior art handlers is also relatively poor due to the use of undersized fasteners therein. As previously indicated, such handlers are also extremely expensive to manufacture and operate due to their incorporation of complex mechanisms with expensive components, such as stepper motors, and the need for skilled calibration and fine tuning.
As previously indicated, perhaps the most significant deficiency of all prior art circuit board handlers is that the circuit boards travel lengthwise (i.e., along their longitudinal axes) therewithin. In this respect, lengthwise or longitudinal travel of over one full length of the circuit board is typically needed in such handlers for each separate handler function, including singulating, testing, sorting, and ejection. Thus, as also previously indicated, the prior art handlers are oversized, which results in shipping and handling problems, set-up problems attributable to the necessity of on-site assembly, the need for excessive floor space (which is often limited), and increased manufacturing costs.
The prior art handlers are also extremely difficult to operate since the operator must often make complex adjustments thereto. In this respect, during a normal day of operation, circuit boards of differing widths will typically be tested within the handler. Accordingly, the magazine tray of the handler must be changed out to match the circuit board width, with the longitudinal travel guide for the circuit board also being adjusted for each width. As previously indicated, the adjustment of the longitudinal travel guide must be precise, and if not exact, causes jamming of the circuit boards within the handler. Additionally, changes in the heights of the circuit boards tested within the handler requires the changeout of a board travel guide which must be precisely relocated in accordance with the circuit board widths.
As also previously indicated, the alignment between the connector pads of the circuit board and the testing fingers of the test connector must be precise. In this respect, the longitudinal movement of the circuit boards in the prior art handlers require such alignment to be provided by a retractable stop and/or sensor. Since the stop is typically a moving part, frequent tuning and readjustment is required between the testing fingers of the test connector and the connector pads of the circuit board. Moreover, the initial installation time and level of training associated with the prior art handlers are extremely high due to their complexity and design. Such complexity limits sales since a sales person must typically accompany the handler for demonstration before any purchase thereof is ultimately made by a buyer.
The longitudinal movement of the circuit boards in the prior art handlers also results in high operating costs due to damage which frequently occurs to the testing fingers of the test connector. In this respect, the testing fingers of the test connector often need replacement due to occurrences of damage thereto. Since in most prior art handlers the circuit board must travel longitudinally a distance of at least four (4) inches in very close proximity to the testing fingers while never contacting them, boards warped even less than 0.050 inches relative to their longitudinal axes are likely to contact the testing fingers, thus resulting in damage thereto. In the prior art handlers, a guide cannot be interfaced to the horizontally oriented surfaces of the circuit board near the connector pads while the circuit boards are traveling under the testing fingers, thus increasing the likelihood that the circuit boards will contact the testing fingers during their travel.
When a circuit board contacts the testing fingers due to the same being warped or due to an improper adjustment in the handler, the testing fingers are bent thereby and thus destroyed. Additionally, the longitudinal movement of the circuit boards in the prior art handlers inherently results in a lack of guidance for the vertical surfaces oriented between the connector pads. In this respect, this vertical edge of the circuit board cannot be guided since it must pass through the testing fingers of the test connector. Such lack of guidance often results in the circuit board contacting and damaging the testing fingers. The high operating costs of the prior art handlers are also attributable to other factors, including circuit boards being damaged due to the stepper motors and conveyors thereof forcing movement during jams. Additionally, such handlers require a dedicated operator and, as previously indicated, require a high level of maintenance.
The prior art handlers are also susceptible to output errors, and often sort in a wrong direction due to the proximity of the circuit board receiving bins thereto. In this respect, since the direction of circuit board travel is lengthwise or longitudinal, receiving bins for collecting good and bad circuit boards are typically located on a common side of the handler in side-by-side or stacked relation to each other. Thus, due to the close proximity of the receiving bins to each other, the continued movement of the conveyor subsequent to the jamming of a circuit board at the sort section often results in the circuit board "jumping" into the wrong receiving bin. The prior art handlers also have limited capabilities, in that the number of circuit board styles which can be tested therein is extremely limited. Additionally, customization for protruding components of the circuit boards or the irregular placement of memory chips is usually not feasible, with there being no insulating spacer under the circuit boards which can be customized. As will be discussed below, the present invention overcomes these and other deficiencies associated with prior art handlers.